The invention relates to a method and apparatus for improving production from an oil well, more specifically, for improving production from a gas lift oil well.
As is well known in the art, gas lift techniques are employed in oil wells which have difficulty in producing satisfactory levels of fluids based on natural formation pressure. Typically, such wells have formation pressure which is not sufficient to drive fluids at an acceptable volume to the surface.
The gas lift technique involves injecting gas into the casing of an oil well through one or more valves, typically located at varying heights along the well. Depending upon the technique being used, the gas may be injected substantially continuously into the column of fluid in the well, thereby lightening this column of fluid so as to enhance the volume of production which can be accomplished with natural formation pressure. Alternatively, gas can be injected intermittently in a repeated or cyclical process so as to produce successive slugs of fluid at the well head.
Although gas lift techniques provide excellent results for certain types of oil wells, each well is different in terms of downhole or formation pressure, downhole or formation temperature, depth to the producing formation, geothermal gradient experienced along the vertical height of the well, and numerous other factors. Thus, determining the optimal operating parameters for a gas lift technique is a time consuming trial and error process which may require extensive supervision and nevertheless provide less than ideal production.
U.S. Pat. No. 4,267,885 to Sanderford is drawn to a method for optimizing production in a continuous or intermittent gas lift well which, through trial and error, increases and/or decreases the volume of gas injected while monitoring the temperature of fluids produced at the surface. According to this method, gas injection is increased and/or decreased as desired so as to provide a maximum possible fluid temperature at the surface. For intermittent production, a similar method is disclosed where the volume of production is monitored per gas injection cycle in an attempt to determine the gas injection volume which will provide maximum possible fluid temperature at the surface. In both cases, a continuous trial and error method is used changing gas injection volumes and waiting to see the effect of such change at the surface. Thus, Sanderford '885 is a trial and error method, and possesses the expected disadvantages for such a method.
In light of the foregoing, it is evident that the need remains for an advantageous method and apparatus for enhancing production from a gas lift well.
It is therefore the primary object of the present invention to provide a method for optimizing production from a gas lift well.
It is a further object of the present invention to provide an apparatus for optimizing production from a gas lift well.
It is a still further object of the present invention to provide a method and apparatus which is readily adaptive to the widely varying conditions experienced at different gas lift wells.
It is another object of the present to provide a method and apparatus which learns well behavior for the specific conditions of a particular well and which controls gas injection and production from the well based upon pattern recognition and past well behavior so as to significantly reduce and/or completely avoid the need for extended or continuous trial and error operation.
Other objects and advantages of the present invention will appear hereinbelow.